`down --volumes` leaves anonymous volumes declared by Dockerfile `VOLUME` instructions behind

[te-horie]

Describe the issue

Note

Related to: #378 (comment)
Unlike the original issue, which concerns down --volumes with selected services, this issue concerns anonymous volumes created by Dockerfile VOLUME instructions during a full down --volumes.

When shutting down the containers for the services defined in compose.yaml with the down --volumes command, podman-compose leaves anonymous volumes behind.
Even if the --volumes option is given, the subsequent volume search cannot find anonymous volumes because they do not have the io.podman.compose.project label.

podman-compose/podman_compose.py

Line 4426 in 4711874

for volume_name in await compose.podman.volume_ls():

In contrast, Docker Compose removes anonymous volumes when it is invoked with down --volumes.

To Reproduce

1. Prepare a sample Dockerfile and compose.yaml as follows:

   FROM busybox:latest
   VOLUME ["/volume-repro"]
   CMD ["sleep", "infinity"]
   

   services:
     busybox:
       init: true
       build:
         context: .
       image: volume-repro
       container_name: volume-repro

2. Execute podman compose down -v to shut down the services, but the anonymous volume declared by VOLUME in the Dockerfile still remains:

   $ podman compose up -d --build
   ...
   $ podman inspect volume-repro | jq -r '.[]|.Mounts|.[]|.Name'
   2d7cea363c6b564d74d2e4221b3a64e3afc5109ed8cc5d6d742ca8d38cc8df49
   $ podman compose --verbose down -v
   ...
   INFO:podman_compose:podman rm volume-repro
   ...
   DEBUG:podman_compose:keep set()
   INFO:podman_compose:['podman', 'volume', 'ls', '--noheading', '--filter', 'label=io.podman.compose.project=podman-compose', '--format', '{{.Name}}']
   ...
   $ podman volume ls
   DRIVER      VOLUME NAME
   local       2d7cea363c6b564d74d2e4221b3a64e3afc5109ed8cc5d6d742ca8d38cc8df49

IMO: Preferable behavior

Anonymous volumes attached to the containers should be removed when the --volumes option is specified.

Actual behavior

The container is removed, but its anonymous volume remains, as shown above.

Possible fix

podman-compose should pass --volumes to podman rm when the --volumes option is specified, as follows:
main...te-horie:podman-compose:down-remove-anonymous-volumes

diff --git a/podman_compose.py b/podman_compose.py
index 3a90cc0..cbc3180 100755
--- a/podman_compose.py
+++ b/podman_compose.py
@@ -4389,7 +4389,7 @@ async def compose_down(compose: PodmanCompose, args: argparse.Namespace) -> None
     for cnt in containers:
         if cnt["_service"] in excluded:
             continue
-        await compose.podman.run([], "rm", [cnt["name"]])
+        await compose.podman.run([], "rm", (["--volumes"] if args.volumes else []) + [cnt["name"]])

     orphaned_images = set()
     if args.remove_orphans:

With this change, the anonymous volume is removed as expected:

$ podman compose up -d --build
...
$ podman inspect volume-repro | jq -r '.[]|.Mounts|.[]|.Name'
38e85348e37272c1e358b3b33a0de92dc8253b83ff57cd4ae31bba6cf85aba2d
$ podman compose --verbose down -v
...
INFO:podman_compose:podman rm --volumes volume-repro
...
DEBUG:podman_compose:keep set()
INFO:podman_compose:['podman', 'volume', 'ls', '--noheading', '--filter', 'label=io.podman.compose.project=podman-compose', '--format', '{{.Name}}']
$ podman volume exists 38e85348e37272c1e358b3b33a0de92dc8253b83ff57cd4ae31bba6cf85aba2d || echo 'NONE'
NONE

Discussion

As @zzgab noted in the previous discussion:

In my opinion, the compatibility with the reference behavior is preferable.

I agree with this opinion.

The help text for compose down also says:

podman-compose/podman_compose.py

Lines 4993 to 4994 in 4711874

	help="Remove named volumes declared in the `volumes` section of the Compose file and "
	"anonymous volumes attached to containers.",

If the help text describes the intended behavior, podman-compose should also remove anonymous volumes created from image VOLUME declarations.
Otherwise, it should clarify that --volumes does not remove this type of anonymous volume.

Please share any comments or opinions on this issue.

Thank you!

Environment:

• OS: WSL
• podman version: 5.8.4
• podman-compose version: 1.6.0 (commit hash: 0f6537e9cfa38f6035ac57c1716b6d55dbaf3ca4)